Most vehicle wheel suspension systems take the form of coiled springs or leaf springs between the wheel axle and vehicle frame for cushioning up and down movements of the wheel in travelling over rough terrain. Normally, shock absorbers are also provided in conjunction with the spring suspension systems for the purpose of absorbing large and sudden shocks to the suspension system.
It is also known in the prior art to provide air cushioning systems for cushioning shocks and up and down movements of a vehicle wheel axis relative to the vehicle frame. Such air suspension type systems as are known are generally of the passive type; that is, they simply rely on the elastic properties of air when compressed. In this respect, the presently known air systems function similarly to springs, and as in the case of springs, shock absorbers would normally be utilized along with the suspension.
A desirable feature of any vehicle wheel suspension system would be an arrangement whereby proper cushioning of the vehicle ride could be accomplished as well as an absorption of sudden and rapid shocks all in one type of suspension thereby avoiding the necessity of auxiliary shock absorbers. Further, it would be desirable to utilize air as the basic cushioning means as opposed to springs since the springs eventually tend to lose their elasticity; that is, the material will actually yield after prolonged use. Moreover, air generally provides a much softer cushion than spring arrangements.
While conventionally known spring suspension systems do function over their lifetime to provide a cushioned ride, there are still problems when a vehicle executes rapid accelerating and decelerating movements or rapid turns. In the case of rapid acceleration particularly when the vehicle is a motorcycle, a very large load is placed on the rear wheel which must be absorbed by the suspension system. Similarly, when decelerating rapidly the load shifts to the front wheel and the front suspension system must absorb this load. The same occurs to a lesser extent in a four-wheel vehicle.
In the case of four-wheel vehicles executing sharp turns, the centrifugal forces generated place a large load on the outside wheels and substantially decrease the load on the inside wheels. Again, any suspension system must be capable of handling these loads.